Electrolytic production of high-purity lithium from low-purity sources
Devices and methods for purifying lithium from lithium salts, including those with low concentration of lithium salts, are provided. A molten composition comprising a lithium salt is electrolyzed with an anode in contact with the molten composition and a cathode separated from the molten composition by a solid electrolyte capable of conducting lithium ions.
1. A method of one-step purification of lithium compounds, comprising electrolyzing a molten composition comprising a lithium salt and an aluminum salt, with an anode at least partially covered by metallic aluminum in contact with the molten composition and a cathode comprising molten lithium separated from the molten composition by a solid electrolyte capable of conducting lithium ions, wherein the solid electrolyte allows lithium ions, but not other atoms, to pass through, and comprises a garnet-type oxide comprises Li 7-x La 3 Ta x Zr 2-x O 12 wherein x is from 0.4 to 0.6, wherein the solid electrolyte has a relative density from 97% to 99.9%, and wherein after the electrolyzing, a concentration of lithium at the cathode is increased by from 7.2 times to over 1500 times at the molten composition.
2. The method of claim 1 , wherein the solid electrolyte is in a form of a cylinder or a plate.
3. The method of claim 2 , wherein the solid electrolyte has a cross-sectional thickness from 0.05 cm to 0.6 cm.
4. The method of claim 2 , wherein the solid electrolyte has a cross-sectional thickness from 0.15 cm to 0.4 cm.
5. The method of claim 1 , wherein the lithium salt comprises LiCl.
6. The method of claim 1 , wherein the molten composition comprises less than 99.7 wt % of the lithium salt.
7. The method of claim 6 , wherein the molten composition comprises less than 97 wt % of the lithium salt.
8. The method of claim 6 , wherein the molten composition comprises less than 50 wt % of the lithium salt.
9. The method of claim 1 , wherein the aluminum salt is AlCl 3 .
10. The method of claim 1 , wherein a mole ratio of lithium to aluminum in the molten composition is from 20:1 to 1:1.
11. An apparatus for one-step purification of lithium compounds, comprising:
an electrolyte compartment for storing a molten electrolyte comprising a lithium salt and an aluminum salt;
an anode comprising metallic aluminum positioned in contact with the molten electrolyte;
a cathode compartment for storing molten lithium;
a solid electrode positioned in contact with the molten lithium;
a solid electrolyte positioned between the electrolyte compartment and the cathode compartment,
wherein the solid electrolyte allows lithium ions, but not any other atoms, to pass through, and comprises a garnet-type oxide comprises Li 7-x La 3 Ta x Zr 2-x O 12 wherein x is from 0.4 to 0.6, wherein the solid electrolyte has a relative density from 97% to 99.9%, and wherein after the purification, the apparatus is configured to increase a lithium concentration in the molten lithium by from 7.2 times to over 1500 times at the molten electrolyte.
12. The apparatus of claim 11 , wherein the molten electrolyte comprises less than 50 wt % of the lithium salt.
13. The apparatus of claim 11 , wherein the solid electrolyte is in a form of a cylinder or a plate.
14. The apparatus of claim 13 , wherein the solid electrolyte has a cross-sectional thickness from 0.05 cm to 0.6 cm.
15. The apparatus of claim 13 , wherein the solid electrolyte has a cross-sectional thickness from 0.15 cm to 0.4 cm.
16. The apparatus of claim 11 , wherein the lithium salt comprises LiCl.
17. The apparatus of claim 11 , wherein the aluminum salt is AlCl 3 .
18. The apparatus of claim 11 , wherein a mole ratio of lithium to aluminum in the molten electrolyte is from 20:1 to 1:1.